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Receiver function (RF) inversion is a well-established method to quantify a horizontally layered approximation of the S-wave velocity structure beneath a seismic station. It is well-known that the RF inverse problem is highly non-unique, and various tools such as joint inversion with other seismological observations exist that may overcome this problem. We present a joint inversion framework along with a Python package that implements the joint inversion of RF and the apparent S-wave velocity (VS,app). Our implementation includes a pseudo-initial model estimation, which helps address the inherent non-uniqueness of the joint inversion of RFs and VS,app. This implementation enhances the resolving power, enabling estimation of S-wave velocities with resolution approaching that of deep controlled source seismic methods. As an illustration, we showcase an example from a permanent station in the Makran subduction zone southeast of the Iranian Plateau and two other stations in the supplementary material. We compare our joint inversion results with several S-wave velocity models obtained through a deep seismic sounding profile and joint inversion of surface wave dispersion and RFs. This comparison shows that although we note a slightly lower sensitivity of our proposed method at greater depths (beyond 50 km), the method yields much better results for shallow structures. Our inversion code provides a powerful, accessible software package that has superior resolving power at shallow depth compared to RFs-surface wave inversion codes. Furthermore, the fact that only one data-derivative is used, makes this inversion code extremely easy to use, without the need for complementary datasets. [ABSTRACT FROM AUTHOR]

The launch of a rocket requires an energy comparable to the energy of many natural processes. For large rockets, the energy release reaches 10–100 TJ, and the power of engines reaches 0.1–1 TW. The energy release per unit volume is much higher than the specific energy content and energy release of all natural processes. During the launch and flight of a large rocket, disturbances in the substratum, the atmosphere, the ionosphere, and even in the magnetosphere occur. Effects from rocket engine burns have been studied for more than 60 years. Research results have been published in hundreds of articles, handbooks, and monographs. It turns out that the effects produced exhibit diverse geophysical phenomena. The effects near the rocket trajectory, namely, the regions of depressed electron density (ionospheric holes), and the generation of infrasound and atmospheric gravity waves (density waves) are investigated better than other effects. Great attention has been paid to studying the geomagnetic effect. The following methods have been used in studies: the Doppler effect, the Faraday, incoherent scattering, ionosonde, magnetometric methods, etc. The effects accompanying the launches and flights of rockets are being actively studied even now. For many years, large-scale (1 to 10 Mm) disturbances that occur after rocket launches have been studied. Their study makes it possible to better understand the mechanisms of the propagation of disturbances from a rocket over global distances, the interaction of subsystems in the Earth–atmosphere–ionosphere–magnetosphere system, and the ecological consequences of rocket engine burns. Disturbances occurring in the atmosphere and geospace substantially depend on the state of the atmospheric–space weather, time of day, season, and phase of the solar cycle. Even with the launch of two identical rockets, disturbances in the mentioned system can be very different. It should be borne in mind that rockets differ in power, trajectories, fuel composition, and the location of cosmodromes. Therefore, studying the response of subsystems to rocket launches and flights remains an urgent problem. The purpose of this study is to describe the results of an analysis of the ionospheric effects of the Soyuz and Proton rockets launched during the 24th cycle of solar activity from the Baikonur Cosmodrome. To observe the effects in the ionosphere caused by the launch of the Soyuz and Proton rockets from the Baikonur Cosmodrome, a vertical sounding Doppler radar was used. As a rule, measurements are carried out at two fixed frequencies of 3.2 and 4.2 MHz. The smaller of them is effective when studying the dynamic processes in the E and F1 layers, and the larger one is effective when studying the F1 and F2 layers. The parameters of ionospheric disturbances that followed the launches of 81 Soyuz rockets and 53 Proton rockets from the Baikonur Cosmodrome in 2009–2021 are analyzed. It is confirmed that there are several groups of delay times for the possible reaction of the ionosphere to the launch and flight of the rockets. These delay times varied widely (from 10 to 300 min). The delay time groups correspond to several groups of apparent horizontal velocities of disturbance propagation (100–200, 390 ± 23 m/s, 0.97 ± 0.10, 1.28 ± 0.13, 1.68 ± 0.13, 2.07 ± 0.13 km/s, and approximately 8 km/s). Slow atmospheric gravity waves, atmospheric gravity waves of man-made origin, density shock waves, slow, and ordinary MHD waves have such velocities. As a rule, the generated perturbations (except for shock waves) are quasi-periodic in behavior with a period in the range from 5 to 20 min. The amplitude of the Doppler shift is 0.1–0.3 Hz. The relative amplitude of quasi-periodic variations in the electron density is typically 1‒10% and rarely reaches 20%. [ABSTRACT FROM AUTHOR]

To understand steeply dipping events in seismic reflection interferometry (SRI), we derived an expression that describes the difference in travel time (Δτ) from a diffractor to two receivers in two dimensions. For a fixed receiver interval, the expression shows that Δτ is zero when the diffractor is at the midpoint of the paired receivers, increases with an apparent velocity of half the medium velocity as the diffractor moves toward either receiver, and remains constant for a diffractor located on the same side of both receivers. The horizontal portion of Δτ is slightly skewed during the normal moveout correction, yielding a maximum peak of the horizontally stacked trace at a slightly smaller time than Δτ. Accordingly, the diffracted waves have an apparent velocity slightly higher than half of the medium velocity in a horizontally stacked image. This conformed to virtual data for an elastic two-layer model with a vertical boundary. We then generalized the expression to three dimensions, in which listric travel time curves were predicted for an oblique edge diffractor, a vertex diffractor offline from the receiver pair, or a buried diffractor. Based on both two- and three-dimensional analyses of the edge diffractor, we tentatively interpreted the linear and listric dipping events observed in the passive SRI image across the Korean Peninsula to have been caused by diffractors near the intersection of the profile and geologic boundaries. [ABSTRACT FROM AUTHOR]

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Depending upon the surface wave methods, the measured surface wave velocities are either normal mode velocities or apparent velocities. The "apparent" surface wave velocity corresponds to the superposed mode combining the available normal modes. The spectral-analysis-of-surface-waves (SASW) method measures the apparent surface wave velocities. However, these velocities render SASW analyses complicated because of the mode jumps induced by several wave groups. To alleviate such complications, this study introduced a beamforming technique and produced information on unwrapped wavenumber, which is vital in unwrapping the phase spectrum in SASW analyses. Additionally, incoming wave directions filtered out multiple reflections and irrelevant seismic events to retain only the surface waves directly propagating from the source. The proposed wavenumber unwrapping technique was verified using field applications, dynamic finite element analysis, and synthetic waveforms. Notably, an optimal beamforming technique was established using four geophones, making the proposed method highly practical and reducing the hardware requirements. Hopefully, the proposed analysis technique provides SASW practitioners with a more comfortable and more reliable environment in utilizing the SASW technique. • Unwrapped wavenumbers were proposed as a guide in SASW velocity calculations. • Wave directions were used as a filter for measured irrelevant stress waves. • Beamforming tests coupled with SASW analysis was optimized by using four receivers. • The proposed method was validated by seismograms, FEA and three field applications. [ABSTRACT FROM AUTHOR]

In this paper the apparent velocity regulation system has been studied and simulated. The objective of this system is to adjust the missile’s fight velocity with the predetermined value, in specified time steps. In fact the apparent velocity regulation system calculates and changes the thrust of the engine (pressure of the combustion chamber) in order to accomplish the desired fight velocity. For this purpose, a dynamic simulation for the propulsion system and also the missile’s flight has been developed. After analyzing the results, it is revealed that using the apparent velocity regulation system; the flight’s range accuracy will be improved dramatically. Comparing two similar missiles, with a same disturbance; one equipped with the apparent velocity regulation system and the other not, revealed that using such a controlling system will keep the accuracy of the target hitting within 200 meters while in the absence of it, the error would be more than 1.5 kilometers